1. Field of the Invention
This invention is related to a engine brake device which can produce a braking force by the operation of means of a compressor impeller.
2. Background Art
There is a proposed apparatus which produces a braking force by a compressor impeller, entitled "Braking Device For a Vehicle Equipped With An Internal Combustion Engine" (Japanese Utility Model Koho No. 26244/1985).
In the above application, as shown in FIG. 2 of the accompanying drawings, an oil pump d includes a drive shaft c and a drive gear b which engaged with a crank gear a, and a gallery cut valve f is disposed in the outlet conduit e of the oil pump d so as to close the oil passage e. The gallery cut valve f is actuated in synchronism with an exhaust brake pressure bearing means, namely an exhaust brake valve (not shown). In FIG. 2, designates a bypass conduit, "h" an impeller of the oil pump d, and "i" an oil pan. According to this idea, upon exhaust braking, in addition to a braking force by the exhaust valve, there is generated another braking force by the impeller h of the oil pump d. With the outlet conduit e closed by the gallery valve f, the impeller h performs a negative work which serve as as a resistance against the crank gear a of the engine via the gear b. In this operation, however, there are some drawbacks. Namely, during the exhaust braking, since the impeller h of the oil pump d produces a resistance force against the crank gear a, the temperature of the oil in the oil pan i becomes to high. This means that an oil cooler should be provided. Further, this construction basically requires oil, which is not favorable as a retarder. Besides, although bypass line g is provided, while the gallery valve f is being closed, the oil supply to the oil pump d might be insufficient.